1. Field of the Invention
The invention relates to a communication system, comprising a network terminal unit coupled via an interface to a bus for connecting terminals to the communication system, the network terminal unit comprising routing means for setting up a local communication between at least two terminals which can be connected to the bus, in response to a first message to be sent over the bus. Furthermore, the invention relates to a network terminal unit to be used in a communication system and also to a terminal to be connected to a communication system. Such a communication system is, for example, a private branch exchange or a subscriber connection to a public integrated services digital network ISDN.
2. Discussion of the Related Art
A communication system as defined in the opening paragraph is known from Japanese Patent Application laid open to public inspection under number 2-79698. In the communication system described there the network terminal unit sets up the local communication between the two terminals if the first message sent by the first terminal and called SET UP message in ISDN contains a telephone number of the second terminal. To ascertain this, the network terminal unit is to comprise a memory containing telephone numbers of all the terminals connected to the bus. The contents of this memory are different for each network terminal unit, because each network terminal unit in a communication system is connected to different terminals which have different telephone numbers. As a result, each network terminal unit is to be programmed in dependence on the terminals connected to the bus, which is undesirable from the point of view of efficiency.